C36 Exhaust opinions

[lamf]

i was thinking of doing 2.75 from headers to muffler, no cats and no resonators. anyone got any opinion on this. will having the 2.75 go all the way to the muffler drop the back pressure? Would it be pointless to do all that and keep the stock resonator? i want it loud but not rice loud.

[benzboy]

OK, the factory piping is 2.75"

DO NOT delete both the cats and the centre res, I know this from experience and it sounds tinny and crap under part throttle (sounds cool at WOT though)

I had it for a few months but it sounded terrible so ended up putting a foot long resonator back in, sounded good after that, not tinny at part load, and was still nice & loud at WOT

If I was to do it again, would probably just cut cat and leave factory res in place.

Here is my dyno vid showing what no cats and the foot long sound like:

Dyno Vid

[lamf]

your video is what made me want to do this. ill just go catless then thanks for the advice

[C230KSPORT00]

From what I was told, If you delete the cats you will smell all of that unburnt fuel when you are idling at a stop light. Along with the people behind you, when you accelerate.

[benzboy]

Originally posted by C230KSPORT00
From what I was told, If you delete the cats you will smell all of that unburnt fuel when you are idling at a stop light. Along with the people behind you, when you accelerate.

Not true at all, if your car was dumping that much unburnt fuel in the exhaust it would ruin the cat anyway (And would also mean your car has issues)

It does smell slightly rich at cold start idle, but as soon as it warms up that goes away.

[omeyhomey]

high flow aftermarket cat will give you more sound one the cam activates (usually 3500-4000rpm+) without giving you tinny sound or annoying low rpm resonance AND it will also help keep environment clean and not make you smell like leaking gas every time you get out of the car or are sitting at a stoplight.

[lamf]

my car sometimes smells like rotting eggs so i think the cats going bad
just wondering what you reccomend for a cat?

[Logic]

the cats are for emissions right? if thats true how does the car pass emissions?

[benzboy]

Originally posted by lamf
my car sometimes smells like rotting eggs so i think the cats going bad
just wondering what you reccomend for a cat?

Pretty sure that means its going bad.

[benzboy]

Originally posted by Logic
the cats are for emissions right? if thats true how does the car pass emissions?

Dont have emissions testing in NZ

[benzboy]

Originally posted by omeyhomey
and not make you smell like leaking gas every time you get out of the car or are sitting at a stoplight.

This does not happen, I have decatted my last 3 cars, and the car before that was old enough to not have a cat from factory.

[C230KSPORT00]

I think if everyone just listened to Omey's advice, they would be happy with the results.

[lamf]

ya my cats are going bad so i wanna hurry up and de-cat it or get some high flowing cats if they arent too much

[omeyhomey]

Originally posted by C230KSPORT00
I think if everyone just listened to Omey's advice, they would be happy with the results.

nobody ever listens to me, the right answer is poking them in the eye and they read over my posts as if its in chineese haha.

[omeyhomey]

metal core high flow cats, they aren't too expensive. :

http://cgi.ebay.com/ebaymotors/2-5-S...3286.m20.l1116

here is another brand:

http://cgi.ebay.com/ebaymotors/High-...3756.m20.l1116


Magnaflow (free shipping):

http://cgi.ebay.com/ebaymotors/59956...3756.m20.l1116


take your pic, can't go wrong with magnaflow plus shipping is free.

Honestly though for secondary cats you can probably go with ceramic cats and be fine, they are dirt cheap (only $37 a pop) same exact body just ceramic internals. Its up to you. If you are replacing primary cats, I would go metallic not ceramic, although I ran ceramic cats on my BMW track car and after tons of abuse they still looked brand new. If your cats are "header huggers" you can't run ceramic, they will melt, but if the cats are in the underbody of the car towards the center of the car (under driver & passenger) then you can get away with ceramic cats no problem.

[omeyhomey]

I highly recommend if you can to just ditch the dual parallel cat setup and run a single race cat, this will greatly increase gas velocity without any drop in back pressure. Those magnaflow race cats are good for 5.9L so it shouldn't pose a problem on the 3.6Ls especially since its way further down the exhaust system than modern day "header hugger" cats. Also you will shed a good 5-10lbs probably as well (stock cats can't be that light).